Page 35 - 2018_IFGC

GENERAL REGULATIONS

For purposes of this calculation, an infiltration rate ducts with the outdoors or spaces that freely communicate
greater than 0.60 ACH shall not be used in Equations 3-1 with the outdoors.
and 3-2. Where directly communicating with the outdoors, or
304.5.3 Indoor opening size and location. Openings used where communicating with the outdoors through vertical
to connect indoor spaces shall be sized and located in ducts, each opening shall have a minimum free area of 1
2
accordance with Sections 304.5.3.1 and 304.5.3.2 (see square inch per 4,000 Btu/h (550 mm /kW) of total input
Figure 304.5.3). rating of all appliances in the enclosure [see Figures
304.5.3.1 Combining spaces on the same story. 304.6.1(1) and 304.6.1(2)].
Where combining spaces on the same story, each open-
ing shall have a minimum free area of 1 square inch per VENTILATION LOUVERS
2
1,000 Btu/h (2200 mm /kW) of the total input rating of CHIMNEY OR GAS VENT (EACH END OF ATTIC)
all appliances in the space, but not less than 100 square
2
inches (0.06 m ). One permanent opening shall com-
mence within 12 inches (305 mm) of the top and one
permanent opening shall commence within 12 inches
(305 mm) of the bottom of the enclosure. The mini-
mum dimension of air openings shall be not less than 3
inches (76 mm). OUTLET AIR
304.5.3.2 Combining spaces in different stories. The
volumes of spaces in different stories shall be consid- ALTERNATE FURNACE
AIR INLET WATER
ered to be communicating spaces where such spaces are OPENING TO HEATER
connected by one or more permanent openings in doors OUTDOORS
or floors having a total minimum free area of 2 square INLET AIR
2
inches per 1,000 Btu/h (4402 mm /kW) of total input
rating of all appliances.
304.6 Outdoor combustion air. Outdoor combustion air
shall be provided through opening(s) to the outdoors in accor-
dance with Section 304.6.1 or 304.6.2. The minimum dimen- VENTILATION LOUVERS
FOR UNHEATED CRAWL SPACE
sion of air openings shall be not less than 3 inches (76 mm).
304.6.1 Two-permanent-openings method. Two perma- FIGURE 304.6.1(1)
nent openings, one commencing within 12 inches (305 ALL AIR FROM OUTDOORS—INLET AIR FROM VENTILATED
mm) of the top and one commencing within 12 inches CRAWL SPACE AND OUTLET AIR TO VENTILATED ATTIC
(see Section 304.6.1)
(305 mm) of the bottom of the enclosure, shall be pro-
vided. The openings shall communicate directly or by
CHIMNEY OR GAS VENT
CHIMNEY OR GAS VENT
VENTILATION LOUVERS
(EACH END OF ATTIC)

OUTLET AIR

FURNACE WATER
OPENING HEATER
FURNACE
WATER INLET AIR DUCT
HEATER [ENDS 1 FOOT
ABOVE FLOOR]

For SI: 1 foot = 304.8 mm.
FIGURE 304.5.3 FIGURE 304.6.1(2)
ALL AIR FROM INSIDE THE BUILDING ALL AIR FROM OUTDOORS THROUGH VENTILATED ATTIC
(see Section 304.5.3) (see Section 304.6.1)

22 2018 INTERNATIONAL FUEL GAS CODE ®
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